Low-sulfur consumable lubricating oil composition and a method of operating an internal combustion engine using the same

ABSTRACT

This invention relates to a low-sulfur consumable lubricating oil composition, comprising: a base oil; an acylated nitrogen-containing compound having a substituent of at least about 10 aliphatic carbon atoms; and a sulfur content of about 5 to about 250 ppm; said composition being characterized by the absence of an extreme-pressure additive comprised of metal and phosphorus.  
     This invention further relates to a a method of operating an internal combustion engine equipped with an exhaust gas aftertreatment device, said method comprising:  
     (A) operating said engine using a normally liquid or gaseous fuel;  
     (B) lubricating said engine using the foregoing low-sulfur consumable lubricating oil composition;  
     (C) removing part of said low-sulfur consumable lubricating oil composition from said engine, said removed part of said low-sulfur consumable lubricating oil composition (i) being combined with said fuel and consumed with said fuel as said engine is operated or (ii) being combined with the exhaust gas from said engine and removed from said engine with said exhaust gas; and  
     (D) adding an additional amount of said low-sulfur consumable lubricating oil composition to said engine to replace said removed part of said low-sulfur consumable lubricating oil composition.

[0001] This application is a continuation-in-part of U.S. applicationSer. No. 09/664,834 filed Sep. 19, 2000. The disclosure in this priorapplication is incorporated herein by reference in its entirety.

TECHNICAL FIELD

[0002] This invention relates to low-sulfur consumable lubricating oilcompositions and to a method of operating an internal combustion engineusing the same. The inventive method provides the advantage of extendingrequired time intervals between oil changes and reducing NO_(x) levelsin exhaust gases.

BACKGROUND OF THE INVENTION

[0003] A problem associated with internal combustion engines equippedwith exhaust gas aftertreatment devices (e.g., catalytic converters,particulate traps, catalyzed traps, etc.) is that the lubricating oilsfor such engines are used in both the crankcase as well as in high wearareas such as the valve train. Because these oils are used in high wearareas they usually contain extreme pressure (EP) agents which typicallycontain metal (e.g., zinc) and phosphorus in order to be effective.During the operation of the engine these EP agents decompose and theresulting decomposition products eventually enter the aftertreatmentdevice resulting in damage to the device. The problem therefore is toprovide a lubricating oil composition that avoids damaging the exhaustgas aftertreatment device.

[0004] Another problem associated with conventional internal combustionengines is that the time interval required between oil changes typicallyis less than the time interval required for other service items such asair filter replacements, coolant changes, brake replacements, and thelike. Oil changes are viewed as one of the most aggravating and, in somecases, most costly maintenance aspects of vehicle ownership.Traditionally, oil change intervals have been extended by base stock andadditive upgrades. Since the 1920s, for example, the extensions havebeen about 15× or greater. Regardless of this progress, the timeintervals required between oil changes continue to lag behind the timeintervals required for other service items. The problem therefore is toimprove the lubricant technology for these engines so that the timeintervals between oil changes can be extended to coincide with otherservice intervals.

[0005] Another problem associated with the operation of internalcombustion engines is that the exhaust gases from such engines containNO_(x) which is an undesirable pollutant. It would be advantageous ifthe level of NO_(x) in the exhaust gases of internal combustion enginescould be reduced.

[0006] The present invention provides a solution to each of theseproblems. With the present invention low-sulfur consumable lubricatingoil compositions characterized by the absence of EP agents containingmetal and phosphorus are used and as a result the exhaust gasaftertreatment device is protected from harmful exposure to such EPagents or their decomposition products. In accordance with the inventivemethod, the required oil change intervals are extended due to the factthat during operation of the engine, used engine oil is continuously orperiodically removed from the engine and replaced with new oil.Unexpectedly, the levels of NO_(x) in exhaust gases from enginesoperating in accordance with the inventive method are reduced.

[0007] U.S. Pat. No. 5,955,403 discloses a sulfur free lubricating oilcomposition which comprises a major portion of a synthetic baselubricating oil and a minor portion of a tri(alkyl phenyl) phosphate ordi(alkylphenyl) phosphoric acid antiwear agent, an amine antioxidant asubstituted succinamide rust inhibitor, and a tolyltriazole. Thetri(alkylphenyl)phosphate antiwear agent is incorporated in the oil inan amount ranging between about 0.1 to 2.0 wt % and the amineantioxidant in amount ranging from about 0.1 to 5 wt %. The succinamideis present in an amount ranging from about 0.01 to 0.5 wt %, and thetolyltriazole from about 0.01 to 0.5 wt %.

[0008] U.S. Pat. No. 4,392,463 discloses a diesel engine having a firstlubrication system, containing conventional engine oil, used tolubricate that section of the engine subjected to excessive wear-thevalve train including the cam shaft, valve lifters, rocker arm, valvestems, etc., and a second lubricant system, utilizing diesel fuel, forlubricating the remaining section of the engine-the crankshaft andassociated parts, pistons, connecting rods, etc. By being exposed tocrankcase blowby exhaust gases, diesel fuel used to lubricate thecrankshaft, etc. absorbs pollutants and contaminants contained thereinand recirculates these contaminants through the fuel system to be burnedand exhausted. By constantly being lubricated with fresh lubricant, wearon these specific parts is reduced. The reference indicates thatfrequent lubrication changes have been eliminated because the dieselfuel/lubricant is continuously changed and circulated through the fuelsystem. Since the engine oil and the first lubrication system is notexposed to crankcase blowby exhausted gases, its useful life isprolonged, thus reducing the frequency of required oil changes.

SUMMARY OF THE INVENTION

[0009] This invention relates to a low-sulfur consumable lubricating oilcomposition, comprising: a base oil; an acylated nitrogen-containingcompound having a substituent of at least about 10 aliphatic carbonatoms; and a sulfur content of about 5 to about 250 ppm; saidcomposition being characterized by the absence of an extreme-pressureadditive containing metal and phosphorus.

[0010] This invention further relates to a a method of operating aninternal combustion engine equipped with an exhaust gas aftertreatmentdevice, said method comprising:

[0011] (A) operating said engine using a normally liquid or gaseousfuel;

[0012] (B) lubricating said engine using the foregoing low-sulfurconsumable lubricating oil composition;

[0013] (C) removing part of said low-sulfur consumable lubricating oilcomposition from said engine, said removed part of said low-sulfurconsumable lubricating oil composition (i) being combined with said fueland consumed with said fuel as said engine is operated or (ii) beingcombined with the exhaust gas from said engine and removed from saidengine with said exhaust gas; and

[0014] (D) adding an additional amount of said low-sulfur consumablelubricating oil composition to said engine to replace said removed partof said low-sulfur consumable lubricating oil composition.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015]FIG. 1 is a schematic illustration of an internal combustionengine that is used in accordance with the inventive method, said enginebeing equipped with an exhaust gas aftertreatment device.

[0016]FIG. 2 is a plot of NO_(x) levels in the exhaust gas generated inthe engine test disclosed in Example 1 using a lubricating oilcomposition within the scope of the invention having a sulfur content of11 ppm.

[0017]FIG. 3 is a plot of NO_(x) levels in the exhaust gas generated inthe engine test disclosed in Example 1 using a lubricating oilcomposition outside the scope of the invention having a sulfur contentof 272 ppm. The engine test which resulted in the data plotted in FIG. 3is disclosed for purposes of comparison.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] The term “low-sulfur” when used to refer to the inventiveconsumable lubricating oil composition means that the lubricating oilcomposition has a sulfur content in the range of about 5 ppm to about250 ppm.

[0019] The term “consumable” when used to refer to the inventivelubricating oil composition means that the oil composition may be either(i) mixed with and consumed with the fuel composition used in theinventive method, or (ii) mixed with the exhaust gas produced during theoperation of the inventive method and removed from the engine with theexhaust gas as the inventive method is performed.

[0020] The term “exhaust gas aftertreatment device” is used herein torefer to any device used in the exhaust gas system of an internalcombustion engine to reduce pollutants in the exhaust gas. These includecatalytic converters, particulate traps, catalyzed traps, and the like.

[0021] The term “sulfur-free” when referring to additives or diluentsfor such additives used with the inventive low-sulfur consumablelubricating oil composition refers to a material that is free ofelemental sulfur or contains an impurity level of elemental sulfur notexceeding about 25 ppm, and in one embodiment not exceeding about 15ppm.

[0022] The term “hydrocarbyl” denotes a group having a carbon atomdirectly attached to the remainder of the molecule and having ahydrocarbon or predominantly hydrocarbon character within the context ofthis invention. Such groups include the following:

[0023] (1) Purely hydrocarbon groups; that is, aliphatic, (e.g., alkylor alkenyl), alicyclic (e.g., cycloalkyl or cycloalkenyl), aromatic,aliphatic- and alicyclic-substituted aromatic, aromatic-substitutedaliphatic and alicyclic groups, and the like, as well as cyclic groupswherein the ring is completed through another portion of the molecule(that is, any two indicated substituents may together form an alicyclicgroup). Such groups are known to those skilled in the art. Examplesinclude methyl, ethyl, octyl, decyl, octadecyl, cyclohexyl, phenyl, etc.

[0024] (2) Substituted hydrocarbon groups; that is, groups containingnon-hydrocarbon substituents which do not alter the predominantlyhydrocarbon character of the group. Those skilled in the art will beaware of suitable substituents. Examples include hydroxy, nitro, cyano,alkoxy, acyl, etc.

[0025] (3) Hetero groups; that is, groups which, while predominantlyhydrocarbon in character, contain atoms other than carbon in a chain orring otherwise composed of carbon atoms. Suitable hetero atoms will beapparent to those skilled in the art and include, for example, nitrogenor oxygen.

[0026] In general, no more than about three substituents or heteroatoms, and preferably no more than one, will be present for each 10carbon atoms in the hydrocarbyl group.

[0027] Terms such as “alkyl-based,” “aryl-based,” and the like havemeanings analogous to the above with respect to alkyl groups, arylgroups and the like.

[0028] The term “hydrocarbon-based” has the same meaning and can be usedinterchangeably with the term hydrocarbyl when referring to moleculargroups having a carbon atom attached directly to the remainder of amolecule.

[0029] The term “lower” as used herein in conjunction with terms such ashydrocarbyl, alkyl, alkenyl, alkoxy, and the like, is intended todescribe such groups which contain a total of up to 7 carbon atoms.

[0030] The term “oil-soluble” refers to a material that is soluble inmineral oil to the extent of at least about one gram per liter at 25° C.

[0031] The Low-sulfur Consumable Lubricating Oil Composition.

[0032] The low-sulfur consumable lubricating oil composition, in oneembodiment, may be comprised of components that add only C, H, O or N tothe lubricating oil composition. In one embodiment, Si may be present.Excluding sulfur, as discussed below, any other elements that may bepresent are present as impurities and as such are at relatively lowconcentrations. The concentration of each of these impurities (prior touse of the oil in the engine) is typically less than about 500 ppm, andin one embodiment less than about 250 ppm, and in one embodiment lessthan about 100 ppm, and in one embodiment less than about 50 ppm, and inone embodiment less than about 25 ppm, and in one embodiment less thanabout 10 ppm. This lubricating oil composition is characterized by theabsence of EP additives comprised of metal (e.g., zinc) and phosphorus.In one embodiment, this lubricating oil composition is characterized bythe absence of detergents or dispersants of the ash-producing type.

[0033] The sulfur in the inventive lubricating oil composition may be inany form. The sulfur may be elemental sulfur or it may present in thelubricating oil composition or added to the lubricating oil compositionas part of a sulfur-containing compound. The sulfur-containing compoundmay be an inorganic sulfur compound or an organic sulfur compound. Thesulfur-containing compound may be a compound containing one or more ofthe groups: sulfamoyl, sulfenamoyl, sulfeno, sulfido, sulfinamoyl,sulfino, sulfinyl, sulfo, sulfonio, sulfonyl, sulfonyldioxy, sulfate,thio, thiocarbamoyl, thiocarbonyl, thiocarbonylamino, thiocarboxy,thiocyanato, thioformyl, thioxo, thioketone, thioaldehyde, thioester,and the like. The sulfur may be present in a hetero group or compoundwhich contains carbon atoms and sulfur atoms (and, optionally, otherhetero atoms such as oxygen or nitrogen) in a chain or ring. Thesulfur-containing compound may be a sulfur oxide such as sulfur dioxideor sulfur trioxide. The sulfur or sulfur-containing compound may beintentionally added to the inventive lubricating oil composition, or itmay be present in the base oil or in one or more of the additives forthe inventive lubricating oil composition as an impurity. The sulfurcontent in the inventive lubricating oil composition is critical and isin the range of about 5 to about 250 ppm, and in one embodiment about 5to about 200 ppm, and in one embodiment about 5 to about 150 ppm, and inone embodiment about 5 to about 100 ppm, and in one embodiment about 5to about 50 ppm, and in one embodiment about 5 to about 25 ppm, and inone embodiment about 5 to about 15 ppm, as measured by inductivelycoupled plasma (ICP) or x-ray techniques.

[0034] The low-sulfur consumable lubricating oil composition iscomprised of one or more base oils which are generally present in amajor amount (i.e. an amount greater than about 50% by weight).Generally, the base oil is present in an amount greater than about 60%,or greater than about 70%, or greater than about 80% by weight of thelubricating oil composition.

[0035] The low-sulfur consumable lubricating oil composition may have aviscosity of up to about 16.3 cSt at 100° C., and in one embodimentabout 5 to about 16.3 cSt at 100° C., and in one embodiment about 6 toabout 13 cSt at 100° C. In one embodiment, the lubricating oilcomposition has an SAE Viscosity Grade of 0W, 0W-20, 0W-30, 0W-40,0W-50, 0W-60, 5W, 5W-20, 5W-30, 5W-40, 5W-50, 5W-60, 10W, 10W-20,10W-30, 10W-40 OR 10W-50.

[0036] The low-sulfur consumable lubricating oil composition may have ahigh-temperature/high-shear viscosity at 150° C. as measured by theprocedure in ASTM D4683 of up to about 4 centipoise, and in oneembodiment up to about 3.7 centipoise, and in one embodiment about 2 toabout 4 centipoise, and in one embodiment about 2.2 to about 3.7centipoise, and in one embodiment about 2.7 to about 3.5 centipoise.

[0037] The base oil used in the low-sulfur consumable lubricating oilcomposition may be a natural oil, synthetic oil or mixture thereof,provided the sulfur content of such oil does not exceed theabove-indicated sulfur concentration limit required for the inventivelow-sulfur lubricating oil composition. The natural oils that are usefulinclude animal oils and vegetable oils (e.g., castor oil, lard oil) aswell as mineral lubricating oils such as liquid petroleum oils andsolvent treated or acid-treated mineral lubricating oils of theparaffinic, naphthenic or mixed paraffinic-naphthenic types. Oilsderived from coal or shale are also useful. Synthetic lubricating oilsinclude hydrocarbon oils such as polymerized and interpolymerizedolefins (e.g., polybutylenes, polypropylenes, propylene isobutylenecopolymers, etc.); poly(1-hexenes), poly-(1-octenes), poly(1-decenes),etc. and mixtures thereof; alkylbenzenes (e.g., dodecylbenzenes,tetradecylbenzenes, dinonylbenzenes, di-(2-ethylhexyl)benzenes, etc.);polyphenyls (e.g., biphenyls, terphenyls, alkylated polyphenyls, etc.);alkylated diphenyl ethers and the derivatives, analogs and homologsthereof and the like.

[0038] Alkylene oxide polymers and interpolymers and derivatives thereofwhere the terminal hydroxyl groups have been modified by esterification,etherification, etc., constitute another class of known syntheticlubricating oils that can be used. These are exemplified by the oilsprepared through polymerization of ethylene oxide or propylene oxide,the alkyl and aryl ethers of these polyoxyalkylene polymers (e.g.,methyl-polyisopropylene glycol ether having an average molecular weightof about 1000, diphenyl ether of polyethylene glycol having a molecularweight of about 500-1000, diethyl ether of polypropylene glycol having amolecular weight of about 1000-1500, etc.) or mono- and polycarboxylicesters thereof, for example, the acetic acid esters, mixed C₃₋₈ fattyacid esters, or the C₁₃Oxo acid diester of tetraethylene glycol.

[0039] Another suitable class of synthetic lubricating oils that can beused comprises the esters of dicarboxylic acids (e.g., phthalic acid,succinic acid, alkyl succinic acids, alkenyl succinic acids, maleicacid, azelaic acid, suberic acid, sebacic acid, fumaric acid, adipicacid, linoleic acid dimer, malonic acid, alkyl malonic acids, alkenylmalonic acids, etc.) with a variety of alcohols (e.g., butyl alcohol,hexyl alcohol, dodecyl alcohol, 2-ethylhexyl alcohol, ethylene glycol,diethylene glycol monoether, propylene glycol, etc.) Specific examplesof these esters include dibutyl adipate, di(2-ethylhexyl) sebacate,di-n-hexyl fumarate, dioctyl sebacate, diisooctyl azelate, diisodecylazelate, dioctyl phthalate, didecyl phthalate, dieicosyl sebacate, the2-ethylhexyl diester of linoleic acid dimer, the complex ester formed byreacting one mole of sebacic acid with two moles of tetraethylene glycoland two moles of 2-ethylhexanoic acid and the like.

[0040] Esters useful as synthetic oils also include those made from C₅to C₁₂ monocarboxylic acids and polyols and polyol ethers such asneopentyl glycol, trimethylol propane, pentaerythritol,dipentaerythritol, tripentaerythritol, etc.

[0041] The oil can be a poly-alpha-olefin (PAO). Typically, the PAOs arederived from monomers having from about 4 to about 30, or from about 4to about 20, or from about 6 to about 16 carbon atoms. Examples ofuseful PAOs include those derived from octene, decene, mixtures thereof,and the like. These PAOs may have a viscosity from about 2 to about 15,or from about 3 to about 12, or from about 4 to about 8 cSt at 100° C.Examples of useful PAOs include 4 cSt at 100° C. poly-alpha-olefins, 6cSt at 100° C. poly-alpha-olefins, and mixtures thereof. Mixtures ofmineral oil with one or more of the foregoing PAOs may be used.

[0042] Unrefined, refined and rerefined oils, either natural orsynthetic (as well as mixtures of two or more of any of these) of thetype disclosed hereinabove can be used in the lubricants of the presentinvention. Unrefined oils are those obtained directly from a natural orsynthetic source without further purification treatment. For example, ashale oil obtained directly from retorting operations, a petroleum oilobtained directly from primary distillation or ester oil obtaineddirectly from an esterification process and used without furthertreatment would be an unrefined oil. Refined oils are similar to theunrefined oils except they have been further treated in one or morepurification steps to improve one or more properties. Many suchpurification techniques are known to those skilled in the art such assolvent extraction, secondary distillation, acid or base extraction,filtration, percolation, etc. Rerefined oils are obtained by processessimilar to those used to obtain refined oils applied to refined oilswhich have been already used in service. Such rerefined oils are alsoknown as reclaimed or reprocessed oils and often are additionallyprocessed by techniques directed to removal of spent additives and oilbreakdown products.

[0043] The acylated nitrogen-containing compound used in the inventivelow-sulfur consumable lubricating oil composition typically functions asan ashless dispersant. A number of acylated nitrogen-containingcompounds having a substituent of at least about 10 aliphatic carbonatoms and made by reacting a carboxylic acid acylating agent with anamino compound are known to those skilled in the art. In such compoundsthe acylating agent is linked to the amino compound through an imido,amido, amidine or salt linkage. The substituent of at least about 10aliphatic carbon atoms may be in either the carboxylic acid acylatingagent derived portion of the molecule or in the amino compound derivedportion of the molecule. In one embodiment, it is in the acylating agentportion. The acylating agent can vary from formic acid and its acylderivatives to acylating agents having high molecular weight aliphaticsubstituents of up to about 5,000, 10,000 or 20,000 carbon atoms. Theamino compounds are characterized by the presence within their structureof at least one HN< group.

[0044] In one embodiment, the acylating agent is a mono- orpolycarboxylic acid (or reactive equivalent thereof) such as asubstituted succinic or propionic acid and the amino compound is apolyamine or mixture of polyamines, most typically, a mixture ofethylene polyamines. The amine also may be a hydroxyalkyl-substitutedpolyamine. The aliphatic substituent in such acylating agents typicallyaverages at least about 30 or at least about 50 and up to about 400carbon atoms.

[0045] Illustrative hydrocarbon based groups containing at least 10carbon atoms are n-decyl, n-dodecyl, tetrapropylene, n-octadecyl, oleyl,chlorooctadecyl, triicontanyl, etc. Generally, the hydrocarbon-basedsubstituents are made from homo- or interpolymers (e.g., copolymers,terpolymers) of mono- and di-olefins having 2 to 10 carbon atoms, suchas ethylene, propylene, 1-butene, isobutene, butadiene, isoprene,1-hexene, 1-octene, etc. Typically, these olefins are 1-monoolefins. Thesubstituent can also be derived from the halogenated (e.g., chlorinatedor brominated) analogs of such homo- or interpolymers. The substituentcan, however, be made from other sources, such as monomeric highmolecular weight alkenes (e.g., 1-tetracontene) and chlorinated analogsand hydrochlorinated analogs thereof, aliphatic petroleum fractions,particularly paraffin waxes and cracked and chlorinated analogs andhydrochlorinated analogs thereof, white oils, synthetic alkenes such asthose produced by the Ziegler-Natta process (e.g., poly(ethylene)greases) and other sources known to those skilled in the art. Anyunsaturation in the substituent may be reduced or eliminated byhydrogenation according to procedures known in the art.

[0046] The hydrocarbon-based substituents are substantially saturated,that is, they contain no more than one carbon-to-carbon unsaturated bondfor every ten carbon-to-carbon single bonds present. Usually, theycontain no more than one carbon-to-carbon non-aromatic unsaturated bondfor every 50 carbon-to-carbon bonds present.

[0047] The hydrocarbon-based substituents are also substantiallyaliphatic in nature, that is, they contain no more than onenon-aliphatic moiety (cycloalkyl, cycloalkenyl or aromatic) group of 6or less carbon atoms for every 10 carbon atoms in the substituent.Usually, however, the substituents contain no more than one suchnon-aliphatic group for every 50 carbon atoms, and in many cases, theycontain no such non-aliphatic groups at all; that is, the typicalsubstituents are purely aliphatic. Typically, these purely aliphaticsubstituents are alkyl or alkenyl groups.

[0048] Specific examples of the substantially saturatedhydrocarbon-based substituents containing an average of more than about30 carbon atoms are the following:

[0049] a mixture of poly(ethylene/propylene) groups of about 35 to about70 carbon atoms;

[0050] a mixture of the oxidatively or mechanically degradedpoly(ethylene/propylene) groups of about 35 to about 70 carbon atoms; amixture of poly(propylene/1-hexene) groups of about 80 to about 150carbon atoms;

[0051] a mixture of poly(isobutene) groups having an average of about 50to about 200 carbon atoms.

[0052] A useful source of the substituents are poly(isobutene)s obtainedby polymerization of a C₄ refinery stream having a butene content ofabout 35 to about 75 weight percent and isobutene content of about 30 toabout 60 weight percent in the presence of a Lewis acid catalyst such asaluminum trichloride or boron trifluoride. These polybutenes containpredominantly (greater than 80% of total repeating units) isobutenerepeating units of the configuration

[0053] In one embodiment, the substituent is a polyisobutene groupderived from a polyisobutene having a high methylvinylidene isomercontent, that is, at least about 70% methylvinylidene, and in oneembodiment at least about 80% methylvinylidene. Suitable highmethylvinylidene polyisobutenes include those prepared using borontrifluoride catalysts. The preparation of such polyisobutenes in whichthe methylvinylidene isomer comprises a high percentage of the totalolefin composition is described in U.S. Pat. Nos. 4,152,499 and4,605,808, the disclosures of each of which are incorporated herein byreference.

[0054] In one embodiment, the carboxylic acid acylating agent is ahydrocarbon substituted succinic acid or anhydride. The substitutedsuccinic acid or anhydride consists of hydrocarbon-based substituentgroups and succinic groups wherein the substituent groups are derivedfrom a polyalkene, said acid or anhydride being characterized by thepresence within its structure of an average of at least about 0.9succinic group for each equivalent weight of substituent groups, and inone embodiment about 0.9 to about 2.5 succinic groups for eachequivalent weight of substituent groups. The polyalkene generally has anumber average molecular weight ({overscore (M)}n) of at least about700, and in one embodiment about 700 to about 2000, and in oneembodiment about 900 to about 1800. The ratio between the weight averagemolecular weight ({overscore (M)}w) and the ({overscore (M)}n) (that is,the {overscore (M)}w/{overscore (M)}n) can range from about 1 to about10, or about 1.5 to about 5. In one embodiment the polyalkene has an{overscore (M)}w/{overscore (M)}n value of about 2.5 to about 5. Forpurposes of this invention, the number of equivalent weights ofsubstituent groups is deemed to be the number corresponding to thequotient obtained by dividing the {overscore (M)}n value of thepolyalkene from which the substituent is derived into the total weightof the substituent groups present in the substituted succinic acid.Thus, if a substituted succinic acid is characterized by a total weightof substituent group of 40,000 and the {overscore (M)}n value for thepolyalkene from which the substituent groups are derived is 2000, thenthat substituted succinic acylating agent is characterized by a total of20 (40,000/2000=20) equivalent weights of substituent groups.

[0055] In one embodiment the carboxylic acid acylating agent is asubstituted succinic acid or anhydride, said substituted succinic acidor anhydride consisting of hydrocarbon-based substituent groups andsuccinic groups wherein the substituent groups are derived frompolybutene in which at least about 50% of the total units derived frombutenes is derived from isobutylene. The polybutene is characterized byan {overscore (M)}n value of about 1500 to about 2000 and an {overscore(M)}w/{overscore (M)}n value of about 3 to about 4. These acids oranhydrides are characterized by the presence within their structure ofan average of about 1.5 to about 2.5 succinic groups for each equivalentweight of substituent groups.

[0056] In one embodiment the carboxylic acid is at least one substitutedsuccinic acid or anhydride, said substituted succinic acid or anhydrideconsisting of substituent groups and succinic groups wherein thesubstituent groups are derived from polybutene in which at least about50% of the total units derived from butenes is derived from isobutylene.The polybutene has an {overscore (M)}n value of about 800 to about 1200and an {overscore (M)}w/{overscore (M)}n value of about 2 to about 3.The acids or anhydrides are characterized by the presence within theirstructure of an average of about 0.9 to about 1.2 succinic groups foreach equivalent weight of substituent groups.

[0057] The amino compound is characterized by the presence within itsstructure of at least one HN< group and can be a monoamine or polyamine.Mixtures of two or more amino compounds can be used in the reaction withone or more acylating reagents. In one embodiment, the amino compoundcontains at least one primary amino group (i.e., —NH₂) and morepreferably the amine is a polyamine, especially a polyamine containingat least two —NH— groups, either or both of which are primary orsecondary amines. The amines may be aliphatic, cycloaliphatic, aromaticor heterocyclic amines.

[0058] Among the useful amines are the alkylene polyamines, includingthe polyalkylene polyamines. The alkylene polyamines include thoseconforming to the formula

[0059] wherein n is from 1 to about 10; each R is independently ahydrogen atom, a hydrocarbyl group or a hydroxy-substituted oramine-substituted hydrocarbyl group having up to about 30 atoms, or twoR groups on different nitrogen atoms can be joined together to form a Ugroup, with the proviso that at least one R group is a hydrogen atom andU is an alkylene group of about 2 to about 10 carbon atoms. U may beethylene or propylene. Alkylene polyamines where each R is hydrogen oran amino-substituted hydrocarbyl group with the ethylene polyamines andmixtures of ethylene polyamines are useful. Usually n will have anaverage value of from about 2 to about 7. Such alkylene polyaminesinclude methylene polyamine, ethylene polyamines, propylene polyamines,butylene polyamines, pentylene polyamines, hexylene polyamines,heptylene polyamines, etc. The higher homologs of such amines andrelated amino alkyl-substituted piperazines are also included.

[0060] Alkylene polyamines that are useful include ethylene diamine,triethylene tetramine, propylene diamine, trimethylene diamine,hexamethylene diamine, decamethylene diamine, octamethylene diamine,di(heptamethylene) triamine, tripropylene tetramine, tetraethylenepentamine, trimethylene diamine, pentaethylene hexamine,di(trimethylene)triamine, N-(2-aminoethyl)piperazine,1,4-bis(2-aminoethyl)piperazine, and the like. Higher homologs as areobtained by condensing two or more of the above-illustrated alkyleneamines are useful, as are mixtures of two or more of any of theafore-described polyamines.

[0061] Ethylene polyamines, such as those mentioned above, areespecially useful for reasons of cost and effectiveness. Such polyaminesare described in detail under the heading “Diamines and Higher Amines”in The Encyclopedia of Chemical Technology, Second Edition, Kirk andOthmer, Volume 7, pages 27-39, Interscience Publishers, Division of JohnWiley and Sons, 1965, which is hereby incorporated by reference for thedisclosure of useful polyamines. Such compounds are prepared mostconveniently by the reaction of an alkylene chloride with ammonia or byreaction of an ethylene imine with a ring-opening reagent such asammonia, etc. These reactions result in the production of the somewhatcomplex mixtures of alkylene polyamines, including cyclic condensationproducts such as piperazines.

[0062] Other useful types of polyamine mixtures are those resulting fromstripping of the above-described polyamine mixtures. In this instance,lower molecular weight polyamines and volatile contaminants are removedfrom an alkylene polyamine mixture to leave as residue what is oftentermed “polyamine bottoms”. In general, alkylene polyamine bottoms canbe characterized as having less than about 2% by weight, usually lessthan about 1% by weight material boiling below about 200° C. In theinstance of ethylene polyamine bottoms, which are readily available andfound to be quite useful, the bottoms contain less than about 2% byweight total diethylene triamine (DETA) or triethylene tetramine (TETA).A typical sample of such ethylene polyamine bottoms obtained from theDow Chemical Company of Freeport, Tex. designated “E-100” showed aspecific gravity at 15.6° C. of 1.0168, a percent nitrogen by weight of33.15 and a viscosity at 40° C. of 121 centistokes. Gas chromatographyanalysis of such a sample indicates it contains about 0.93% “Light Ends”(most probably DETA), 0.72% TETA, 21.74% tetraethylene pentamine and76.61% pentaethylene hexamine and higher (by weight). These alkylenepolyamine bottoms include cyclic condensation products such aspiperazine and higher analogs of diethylenetriamine,triethylenetetramine and the like.

[0063] These alkylene polyamine bottoms can be reacted solely with theacylating agent, in which case the amino reactant consists essentiallyof alkylene polyamine bottoms, or they can be used with other amines andpolyamines, or alcohols or mixtures thereof. In these latter cases atleast one amino reactant comprises alkylene polyamine bottoms.

[0064] Other polyamines are described in, for example, U.S. Pat. Nos.3,219,666 and 4,234,435, and these patents are hereby incorporated byreference for their disclosures of amines which can be reacted with theacylating agents described above to form useful acylatednitrogen-containing compounds.

[0065] In one embodiment, the amine may be a hydroxyamine. Typically,the hydroxyamines are primary, secondary or tertiary alkanol amines ormixtures thereof. Such amines can be represented by the formulae:

H₂N—R′—OH RN(H)—R′—OH RRN—R′—OH

[0066] wherein each R is independently a hydrocarbyl group of one toabout eight carbon atoms or hydroxyhydrocarbyl group of two to abouteight carbon atoms, preferably one to about four, and R′ is a divalenthydrocarbyl group of about two to about 18 carbon atoms, preferably twoto about four. The group —R′—OH in such formulae represents thehydroxyhydrocarbyl group. R′ can be an acyclic, alicyclic or aromaticgroup. Typically, R′ is an acyclic straight or branched alkylene groupsuch as an ethylene, 1,2-propylene, 1,2-butylene, 1,2-octadecylene, etc.group. Where two R groups are present in the same molecule they can bejoined by a direct carbon-to-carbon bond or through a heteroatom (e.g.,oxygen or nitrogen) to form a 5-, 6-, 7- or 8-membered ring structure.Examples of such heterocyclic amines include N-(hydroxyl loweralkyl)-morpholines, -piperidines, -oxazolidines, and the like.Typically, however, each R′ is independently a methyl, ethyl, propyl,butyl, pentyl or hexyl group.

[0067] Examples of these alkanolamines include mono-, di-, andtriethanol amine, diethylethanolamine, ethylethanolamine,butyldiethanolamine, etc.

[0068] The hydroxyamines can also be an etherN-(hydroxyhydrocarbyl)-amine. These are hydroxypoly(hydrocarbyloxy)analogs of the above-described hydroxy amines (these analogs alsoinclude hydroxyl-substituted oxyalkylene analogs). SuchN-(hydroxyhydrocarbyl) amines can be conveniently prepared by reactionof epoxides with afore-described amines and can be represented by theformulae:

N₂N—(R′O)_(x)—H RN(H)—(R′O)_(x)H RRN—(R′O)_(x)H

[0069] wherein x is a number from about 2 to about 15 and R and R′ areas described above. R may also be a hydroxypoly(hydrocarbyloxy) group.

[0070] The acylated nitrogen-containing compounds include amine salts,amides, imides, amidines, amidic acids, amidic salts and imidazolines aswell as mixtures thereof. To prepare the acylated nitrogen-containingcompounds from the acylating reagents and the amino compounds, one ormore acylating reagents and one or more amino compounds are heated,optionally in the presence of a normally liquid, substantially inertorganic liquid solvent/diluent, at temperatures in the range of about80° C. up to the decomposition point of either the reactants or thecarboxylic derivative but normally at temperatures in the range of about100° C. up to about 30020 C. provided 300° C. does not exceed thedecomposition point. Temperatures of about 125° C. to about 250° C. arenormally used. The acylating reagent and the amino compound are reactedin amounts sufficient to provide from about one-half equivalent up toabout 2 moles of amino compound per equivalent of acylating reagent.

[0071] Many patents have described useful acylated nitrogen-containingcompounds including U.S. Pat. No. 3,172,892; 3,219,666; 3,272,746;3,310,492; 3,341,542; 3,444,170; 3,455,831; 3,455,832; 3,576,743;3,630,904; 3,632,511; 3,804,763; and 4,234,435. A typical acylatednitrogen-containing compound of this class is that made by reacting apoly(isobutene)-substituted succinic acid acylating agent (e.g.,anhydride, acid, ester, etc.) wherein the poly(isobutene) substituenthas between about 50 to about 400 carbon atoms with a mixture ofethylenepolyamines having about 3 to about 7 amino nitrogen atoms perethylenepolyamine and about 1 to about 6 ethylene units. The above-notedU.S. patents are hereby incorporated by reference for their disclosureof acylated amino compounds and their method of preparation.

[0072] Another type of acylated nitrogen-containing compound belongingto this class is that made by reacting a carboxylic acid acylating agentwith a polyamine, wherein the polyamine is the product made bycondensing a hydroxy material with an amine. These compounds aredescribed in U.S. Pat. No. 5,053,152 which is incorporated herein byreference for its disclosure of such compounds.

[0073] Another type of acylated nitrogen-containing compound belongingto this class is that made by reacting the afore-describedalkyleneamines with the afore-described substituted succinic acids oranhydrides and aliphatic monocarboxylic acids having from 2 to about 22carbon atoms. In these types of acylated nitrogen compounds, the moleratio of succinic acid to monocarboxylic acid ranges from about 1:0.1 toabout 1:1. Typical of the monocarboxylic acid are formic acid, aceticacid, dodecanoic acid, butanoic acid, oleic acid, stearic acid, thecommercial mixture of stearic acid isomers known as isostearic acid,tall oil acid, etc. Such materials are more fully described in U.S. Pat.Nos. 3,216,936 and 3,250,715 which are hereby incorporated by referencefor their disclosures in this regard.

[0074] Still another type of acylated nitrogen-containing compound thatmay be useful is the product of the reaction of a fatty monocarboxylicacid of about 12-30 carbon atoms and the afore-described alkyleneamines,typically, ethylene-, propylene- or trimethylenepolyamines containing 2to 8 amino groups and mixtures thereof. The fatty monocarboxylic acidsare generally mixtures of straight and branched chain fatty carboxylicacids containing 12-30 carbon atoms. A widely used type of acylatednitrogen compound is made by reacting the afore-describedalkylenepolyamines with a mixture of fatty acids having from 5 to about30 mole percent straight chain acid and about 70 to about 95% molebranched chain fatty acids. Among the commercially available mixturesare those known widely in the trade as isostearic acid. These mixturesare produced as a by-product from the dimerization of unsaturated fattyacids as described in U.S. Pat. Nos. 2,812,342 and 3,260,671.

[0075] The branched chain fatty acids can also include those in whichthe branch is not alkyl in nature, such as found in phenyl andcyclohexyl stearic acid and the chloro-stearic acids. Branched chainfatty carboxylic acid/alkylene polyamine products have been describedextensively in the art. See for example, U.S. Pat. Nos. 3,110,673;3,251,853; 3,326,801; 3,337,459; 3,405,064; 3,429,674; 3,468,639;3,857,791. These patents are hereby incorporated by reference for theirdisclosure of fatty acid/polyamine condensates for use in lubricatingoil formulations.

[0076] In one embodiment, the inventive low-sulfur consumablelubricating oil composition is characterized by a chlorine level of nomore than about 10 ppm, and in one embodiment no more than about 7 ppm,and in one embodiment no more than about 5 ppm. This necessitates thatthe acylated nitrogen-containing compound be chlorine-free or containsuch low chlorine levels that the addition of such compound to thelubricating oil composition results in the formation of a lubricatingoil composition with a chlorine level of no more than about 10 ppm. Inone embodiment, the acylated nitrogen-containing compound has a chlorinecontent of no more than about 50 ppm, and in one embodiment no more thanabout 25 ppm, and in one embodiment no more than about 10 ppm. In oneembodiment, the acylated nitrogen-containing compound is chlorine free.

[0077] The acylated nitrogen-containing compound is typically employedin the low-sulfur consumable lubricating oil composition at aconcentration in the range of about 1% to about 25% percent by weight,and in one embodiment about 5% to about 15% by weight. These compoundscan be added directly to the lubricating oil composition. In oneembodiment, however, they are diluted with a substantially inert,normally liquid organic diluent such as mineral oil, naphtha, benzene,toluene or xylene to form an additive concentrate. These concentratesusually contain from about 1% to about 99% by weight, and in oneembodiment about 10% to about 90% by weight of the diluent. In oneembodiment, the organic diluent is a sulfur-free composition.

[0078] An advantage of the inventive low-sulfur consumable lubricatingoil compositions is that these oil compositions may be easier to disposeof from an environmental perspective than conventional lubricating oils.This is due to the absence of EP additives containing phosphorus andmetal in these lubricating oil compositions. Conventional lubricatingoil compositions, on the other hand, typically contain relatively highconcentrations of such EP additives.

[0079] The low-sulfur consumable lubricating oil composition maycontain, in addition to the base oil, sulfur and acylatednitrogen-containing compounds referred to above, one or more detergentsor dispersants of the ashless type. The ashless detergents anddispersants are so called despite the fact that, depending on theirconstitution, they may upon combustion yield a non-volatile materialsuch as boric oxide; however, they do not ordinarily contain metal andtherefore do not yield a metal-containing ash on combustion. Many typesare known in the art, and are suitable for use in these lubricating oilcompositions. These include the following:

[0080] (1) Reaction products of carboxylic acids (or derivativesthereof) containing at least about 34, and in one embodiment at leastabout 54 carbon atoms, with organic hydroxy compounds such as phenolsand alcohols, and/or basic inorganic materials. Examples of these“carboxylic dispersants” are described in many U.S. Pat. Nos. including3,219,666; 4,234,435; and 4,938,881.

[0081] (2) Reaction products of relatively high molecular weightaliphatic or alicyclic halides with amines, preferably oxyalkylenepolyamines. These may be characterized as “amine dispersants” andexamples thereof are described for example, in the following U.S. Pat.Nos. 3,275,554; 3,438,757; 3,454,555; and 3,565,804.

[0082] (3) Reaction products of alkyl phenols in which the alkyl groupcontains at least about 30 carbon atoms with aldehydes (especiallyformaldehyde) and amines (especially polyalkylene polyamines), which maybe characterized as “Mannich dispersants.” The materials described inthe following U.S. patemts are illustrative: U.S. Pat. Nos. 3,649,229;3,697,574; 3,725,277; 3,725,480; 3,726,882; and 3,980,569.

[0083] (4) Products obtained by post-treating the amine or Mannichdispersants with such reagents as urea, aldehydes, ketones, carboxylicacids, hydrocarbon-substituted succinic an hydrides, nitrites, epoxides,boron compounds, phosphorus compounds or the like. Exemplary materialsof this kind are described in the following U.S. Pat. Nos. 3,639,242;3,649,229; 3,649,659; 3,658,836; 3,697,574; 3,702,757; 3,703,536;3,704,308; and 3,708,422.

[0084] (5) Interpolymers of oil-solubilizing monomers such as decylmethacrylate, vinyl decyl ether and high molecular weight olefins withmonomers containing polar substituents, e.g., aminoalkyl acrylates oracrylamides and poly-(oxyethylene)-substituted acrylates. These may becharacterized as “polymeric dispersants” and examples thereof aredisclosed in the following U.S. Pat. Nos. 3,329,658; 3,449,250;3,519,565; 3,666,730; 3,687,849; and 3,702,300.

[0085] The above-noted patents are incorporated by reference herein fortheir disclosures of ashless dispersants.

[0086] The low-sulfur consumable lubricating oil composition may alsocontain other lubricant additives known in the art. These include, forexample, corrosion-inhibiting agents, antioxidants, viscosity modifiers,pour point depressants, friction modifiers, fluidity modifiers,anti-foam agents, etc.

[0087] Pour point depressants are used to improve the low temperatureproperties of oil-based compositions. See, for example, page 8 of“Lubricant Additives” by C. V. Smalheer and R. Kennedy Smith (LeziusHiles Co. publishers, Cleveland, Ohio, 1967). Examples of useful pourpoint depressants are polymethacrylates; polyacrylates; polyacrylamides;condensation products of haloparaffin waxes and aromatic compounds;vinyl carboxylate polymers; and terpolymers of dialkylfumarates, vinylesters of fatty acids and alkyl vinyl ethers. Pour point depressants aredescribed in U.S. Pat. Nos. 2,387,501; 2,015,748; 2,655,479; 1,815,022;2,191,498; 2,666,746; 2,721,877; 2,721,878; and 3,250,715 which areherein incorporated by reference for their relevant disclosures.

[0088] Anti-foam agents are used to reduce or prevent the formation ofstable foam. Typical anti-foam agents include silicones or organicpolymers. Additional antifoam compositions are described in “FoamControl Agents,” by Henry T. Kerner (Noyes Data Corporation, 1976),pages 125-162.

[0089] Each of the foregoing additives, when used, is used at afunctionally effective amount to impart the desired properties to thelubricant. Thus, for example, if an additive is a corrosion inhibitor, afunctionally effective amount of this corrosion inhibitor would be anamount sufficient to impart the desired corrosion inhibitioncharacteristics to the lubricant. Generally, the concentration of eachof these additives, when used, ranges from about 0.001% to about 20% byweight, and in one embodiment about 0.01% to about 10% by weight basedon the total weight of the low-sulfur consumable lubricating oilcomposition.

[0090] These additives can be added directly to the low-sulfurconsumable lubricating oil composition. In one embodiment, however, theyare diluted with a substantially inert, normally liquid organic diluentsuch as mineral oil, naphtha, benzene, toluene or xylene to form anadditive concentrate. These concentrates usually contain from about 1%to about 99% by weight, and in one embodiment about 10% to about 90% byweight of such diluent. In one embodiment, this diluent is a sulfur-freecomposition.

[0091] Method of Operating Internal Combustion Engine

[0092] The inventive method will be initially discussed with referenceto FIG. 1. The engine 10 may be a spark ignition internal combustionengine, which may be referred to as a gasoline powered engine, orcompression ignition internal combustion engine, which may be referredto as a diesel engine. The spark ignition engine may be a four-strokeinternal combustion engine.

[0093] The engine 10 may employ a split lubrication system where thehigh-wear areas or components of the engine are lubricated using aconventional lubricating oil composition, and the crankcase islubricated using the inventive low-sulfur consumable lubricating oilcomposition. The high-wear areas lubricated using a conventionallubricating oil composition include the valve train (including the camshaft and associated parts such as cam lobes, tappets, followers, valvetips, rocker arms, rocker arm mechanisms, and the like). The crankcaselubricated using the inventive low-sulfur consumable lubricating oilcomposition may include the crankshaft and associated parts, pistons,connecting rods, and the like. Engines employing split lubricationsystems of this type are disclosed in U.S. Pat. Nos. 4,392,463;5,195,474; and 5,709,186; and French Patent 2,605,677. These patents areincorporated herein by reference for their disclosure of enginesemploying split lubrication systems.

[0094] The engine 10 may be lubricated in the high-wear areas using asolid film lubricant and in the remaining areas using the inventivelow-sulfur consumable lubricating oil composition. The high-wear areasmay be lubricated using a combination of a solid film lubricant and theinventive low-sulfur consumable lubricating oil composition. The solidfilm lubricant may be any solid film lubricant that provides enhancedwear resistance characteristics and enhanced lubricity characteristicswhen applied to wear interfaces or contacts as compared to when thesolid film lubricant is not present. The solid film lubricant may have afilm thickness of about 5 to about 100 microns, and in one embodimentabout 5 to about 75 microns. The solid film lubricant may be applied tothe desired engine components by the engine manufacturer. Among the highwear areas or components of the engines that may be so lubricated arewear interfaces or contacts in the valve train. These include the wearinterfaces or contacts of the cam lobes, tappets, followers, valve tips,rocker arms, rocker arm mechanisms, and the like. Additional enginecomponents that may be lubricated in this manner include the wearinterfaces or contacts of the cylinder bores, cylinder walls, pistonrings, skirts, bearings, connecting rods, and the like. Included amongthe solid film lubricants that may be used are those disclosed in U.S.Pat. No. 5,482,637 which discloses solid film lubricants comprised of atleast two solid lubricants selected from graphite, MoS₂, and BN. U.S.Pat. No. 5,358,753 discloses solid film lubricants comprised of graphiteand MoS₂. International Publication WO 97/13884 discloses a compositecoating of a metal and an oxide of the metal wherein the oxide has alower oxygen content than any of the metal's oxide forms, the metalbeing selected from Ni, Cu, Mo, Fe or an alloy thereof. German Patent DE195 48 718 C1 discloses solid film lubricants comprised of a metal oxidecoating wherein the metal is Ti, Al, Mo, V or Cr. The solid filmlubricant may be a carbon coating that is applied under vacuum by alaser. The foregoing patents are incorporated herein by reference fortheir disclosures of solid film lubricants.

[0095] The engine 10 may be a camless internal combustion engine.Camless internal combustion engines do not employ a camshaft forcontrolling the timing and lifting of the engine's intake and exhaustvalves. These engines typically employ intake valves and exhaust valvesthat are electrically actuated, hydraulically actuated orelectrohydraulically actuated. Examples of such engines are disclosed inU.S. Pat. Nos. 5,255,641; 5,311,711; 5,367,990; 5,373,817; 5,377,631;5,404,844; 5,419,301; 5,456,221; 5,456,222, 5,562,070; 5,572,961;5,615,646; 5,619,965; 5,694,893; 5,709,178; 5,758,625; 5,970,956; and6,024,060, which are incorporated by reference for their disclosures ofcamless engines.

[0096] The engine 10 includes a crankcase 12, and a fuel system 14,which includes a fuel tank, fuel pump, fuel injectors, fuel filter, andthe like. The fuel mixes with air, and undergoes combustion in thecombustion chambers of the engine. An exhaust gas is removed from theengine as indicated by arrow 16. An exhaust gas aftertreatment device 18(e.g., catalytic converter, particulate trap, catalyzed trap, and thelike) and an exhaust muffler 20 are provided as part of an exhaustsystem for removing exhaust gas from the engine. The engine 10 includesa pump (not shown) for circulating oil throughout the engine and an oilsump 22. The engine 10 is equipped with a make-up oil reservoir 24 and apump or metering device 26 for advancing new oil from the make-up oilreservoir 24 to the crankcase 12.

[0097] The engine 10 operates in the normal sequence with the fuel beingadvanced from the fuel system 14 to the combustion chambers of theengine where a mixture of the fuel and air undergoes combustion. Theexhaust gas from the engine is removed through the exhaust gasaftertreatment device 18 and exhaust muffler 20. During the operation ofthis engine, the low-sulfur consumable lubricating oil compositioncirculates through the engine in the normal manner lubricating thedesired engine components. A portion of the low-sulfur consumablelubricating oil composition used in the engine collects in oil sump 22,and is pumped from oil sump 22 to fuel system 14, as indicated bydirectional arrow 28, where it is combined with the fuel. Theintroduction of the oil into the fuel may occur in one or more of thefuel tank, fuel return line, fuel injectors, intake manifold, positivecrankcase ventilation (PCV) system, exhaust gas recirculation (EGR)system, intake and/or exhaust valve guides, or air intake system of theengine 10.

[0098] The resulting combination of fuel and oil is comprised of about0.01% to about 5% by weight of said oil, and in one embodiment about0.05% to about 3% by weight, and in one embodiment about 0.1% to about1.5% by weight, and in one embodiment about 0.1% to about 1% by weight,and in one embodiment about 0.1% to about 0.7% by weight, and in oneembodiment about 0.1% to about 0.5% by weight, and in one embodimentabout 0.2% to about 0.3% by weight of said oil, with the remainder beingfuel.

[0099] Alternatively (as shown in the dashed line 30 in FIG. 1), theportion of the low-sulfur consumable lubricating oil composition removedfrom the oil sump 22 may be advanced to the exhaust gas system where itis combined with the exhaust gas at any point in the exhaust gas systemupstream of (i.e., prior to entry into) the exhaust gas aftertreatmentdevice 18.

[0100] The sequence of removing used oil from the engine and replacingit with new oil may be performed continuously or intermittently duringthe operation of the engine.

[0101] The fuel may be a normally liquid or gaseous fuel. These includehydrocarbonaceous petroleum distillate fuels such as motor gasoline asdefined by ASTM Specification D439 and diesel fuel as defined by ASTMSpecification D396. Normally liquid hydrocarbon fuels containingmaterials such as alcohols, ethers, organo-nitro compounds and the like(e.g., methanol, ethanol, diethyl ether, methyl ethyl ether,nitromethane) are also within the scope of this invention as are liquidfuels derived from vegetable or mineral sources such as corn, alfalfa,shale and coal. Examples of such mixtures include gasoline and ethanol,and diesel fuel and ether.

[0102] In one embodiment, the fuel is gasoline, that is, a mixture ofhydrocarbons having an ASTM distillation range from about 60° C. at the10% distillation point to about 205° C. at the 90% distillation point.In one embodiment, the gasoline fuel composition is an unleaded fuelcomposition. In one embodiment, the gasoline is a chlorine-free orlow-chlorine gasoline characterized by a chlorine content of no morethan about 10 ppm. In one embodiment, the gasoline is a low-sulfur fuelcharacterized by a sulfur content of no more than about 300 ppm, and inone embodiment no more than about 150 ppm, and in one embodiment no morethan about 100 ppm, and in one embodiment no more than about 50 ppm, andin one embodiment no more than about 25 ppm, and in one embodiment nomore than about 10 ppm.

[0103] The diesel fuel that is useful may be any diesel fuel. Thesediesel fuels typically have a 90% point distillation temperature in therange of about 300° C. to about 390° C., and in one embodiment about330° C. to about 350° C. The viscosity for these fuels typically rangesfrom about 1.3 to about 24 centistokes at 40° C. The diesel fuels can beclassified as any of Grade Nos. 1-D, 2-D or 4-D as specified in ASTMD975. These diesel fuels may contain alcohols and esters. In oneembodiment the diesel fuel has a sulfur content of up to about 0.05% byweight (low-sulfur diesel fuel) as determined by the test methodspecified in ASTM D2622-87.

[0104] The fuel compositions may contain one or more fuel additivesknown in the art for enhancing the performance of the fuel. Theseinclude deposit preventers or modifiers, dyes, cetane improvers,antioxidants such as 2,6-di-tertiary-butyl-4-methyl-phenol, corrosioninhibitors such as alkylated succinic acids and anhydrides,bacteriostatic agents, gum inhibitors, metal deactivators, demulsifiers,upper cylinder lubricants, anti-icing agents, ashless dispersants, andthe like.

[0105] The fuel additives may be added directly to the fuel, or they maybe diluted with a normally liquid organic diluent such as naphtha,benzene, toluene, or xylene to form an additive concentrate prior toaddition to the fuel. These concentrates typically contain from about10% to about 90% by weight diluent.

[0106] The fuel may be a gaseous fuel such as natural gas. The fuel maybe stored as a liquid and used in its gaseous form. Examples includepropane and dimethyl ether.

EXAMPLE 1

[0107] Engine tests are conducted using a 2.3 liter, overhead cam,four-cylinder Ford electronic fuel injected engine. The engine isoperated at low- and mid-range speeds and temperatures for 288 hours,simulating stop-and-go urban and moderate freeway driving. The testconditions involve 72 cycles, each being 4 hours in length and having 3stages, for a total test time of 288 hours. The length of time andoperating conditions for each stage is as follows: Speed Load CoolantStage Hours (ppm) (kW) Oil (° C.) (° C.) 1 2.00 2500 25.0 68.3 51.7 21.25 2500 25.0 98.9 85.0 3 0.75 750 0.7 46.1 46.1

[0108] The valve train (i.e, cam shaft, valve lifters, rocker arms,valve stems, etc.) is separated from the crankcase (i.e., crankshaft,pistons, connecting rods, etc.) to simulate a split engine design. Thestandard Cu-Pb bearings are replaced with Al—Sn bearings. A JohnsonMatthey JM220K catalyst is installed in the exhaust system.

[0109] The fuel is an unleaded gasoline fuel composition having a sulfurcontent of 28 ppm. The valve train is lubricated using a conventionallubricating oil composition. The crankcase is lubricated using thefollowing lubricating oil compositions (in the table below all numericalvalues provided for the components of the composition (except the foaminhibitor) are in percent by weight). A B Base oil - - SAE 5W-30Polyalpha olefin oil mixture 83.4 83.4 (80% by wt. polyalphaolefinhaving viscosity of 6 cSt @ 100° C. and 20% by wt. polyalphaolefinhaving viscosity of 4 cSt 100° C.) Dispersant - - Succinimide derivedfrom high 14.3 — vinylidene polyisobutene (number average molecularweight (Mn) equal to about 1000) substituted succinic anhydride andtetraethylene pentamine (Nitrogen content = 3.3% by wt.) dispersed inoil (40% by wt. sulfur-free 100N (neutral) mineral oil) Dispersant - -Succinimide derived from high — 14.3 vinylidene polyisobutene (Mn equalto about 1000) substituted succinic anhydride and tetraethylenepentamine (Nitrogen content = 3.3% by wt.) dispersed in oil (40% by wt.100N mineral oil) Viscosity modifier - - LZ 7067 (a product of Lubrizol0.8 0.8 identified as an olefin copolymer) Diluent oil (sulfur-free 100Nmineral oil) 0.38 — Diluent oil (100N mineral oil) — 0.38 Corrosioninhibitor - - Pluradyne FL11 (product of 0.02 0.02 BASF identified as anethylene oxide-propylene oxide copolymer) Antioxidant - - Nonylateddiphenylamine 0.6 0.6 Antioxidant - - 4,4′-methylene bis 2,6-di-t-butylphenol 0.5 0.5 Foam inhibitor - - Polydimethyl siloxane dispersed in 50ppm 50 ppm kerosene (90% kerosene) Physical properties: Viscosity @ 100°C., cSt 11.43 11.59 Viscosity @ 40° C., cSt 68.20 70.71 Viscosity index162 159 High Temperature/High Sheer @ 150° C., cP 3.50 3.46 (ASTM D4683) Chemical properties: % P, Zn, Si, Ca, Mg, Na, Halogen nil nil % N,wt % 0.492 0.492 Si, ppm 2 2 S, ppm 11 272

[0110] The gasoline fuel composition contains 0.5% by weight of afreshly blended sample of the foregoing lubricating oil composition A.Oil is removed from the crankcase in quantities equivalent to the oilconsumed with the fuel. The fuel usage per 24 hour interval is 110liters, the oil content being 0.55 liter. At 24 hour intervals, 0.71liter samples of crankcase oil are removed, and replaced with 0.54 literof new oil plus 0.17 liter of the removed sample. The NO_(x) level inthe exhaust gas is measured before entering the catalyst and afterpassing through the catalyst with the results being plotted in FIG. 2.

[0111] The foregoing engine test is repeated except that theabove-indicated lubricating oil composition B is used instead of oilcomposition A. This test is provided for comparative purposes. TheNO_(x) level in the exhaust gas before entering the catalyst as well asafter passing through the catalyst is plotted in FIG. 3.

[0112] The foregoing illustrates an advantage of the inventive methodwhich is to provide a low level of NO_(x) in the exhaust gas of aninternal combustion engine equipped with an exhaust gas aftertreatmentdevice.

[0113] While the invention has been explained in relation to itspreferred embodiments, it is to be understood that various modificationsthereof will become apparent to those skilled in the art upon readingthe specification. Therefore, it is to be understood that the inventiondisclosed herein is intended to cover such modifications as fall withinthe scope of the appended claims.

1. A low-sulfur consumable lubricating oil composition, comprising: abase oil; an acylated nitrogen-containing compound having a substituentof at least about 10 aliphatic carbon atoms; and a sulfur content ofabout 5 to about 250 ppm; said composition being characterized by theabsence of an extreme-pressure additive comprised of metal andphosphorus.
 2. The composition of claim 1 wherein said lubricating oilcomposition is comprised of components that add only C, H, O or N, andoptionally Si to said composition.
 3. The composition of claim 1 whereinsaid low-sulfur consumable lubricating oil composition has a viscosityof up to about 16.3 cSt at 100° C.
 4. The composition of claim 1 whereinsaid low-sulfur consumable lubricating oil composition has an SAEViscosity Grade of 0W, 0W-20, 0W-30, 0W-40, 0W-50, 0W-60, 5W, 5W-20,5W-30, 5W-40, 5W-50, 5W-60, 10W, 10W-20, 10W-30, 10W-40 or 10W-50. 5.The composition of claim 1 wherein said low-sulfur consumablelubricating oil composition has a high-temperature/high-shear viscosityat 150° C. of up to about 4 centipoise.
 6. The composition of claim 1wherein said low-sulfur consumable lubricating oil composition iscomprised of a mineral base oil.
 7. The composition of claim 1 whereinsaid low-sulfur consumable lubricating oil composition is comprised of apoly-alpha-olefin base oil.
 8. The composition of claim 1 wherein saidacylated nitrogen-containing compound is derived from a carboxylicacylating agent and at least one amino compound containing at least one—NH— group, said acylating agent being linked to said amino compoundthrough an imido, amido, amidine or salt linkage.
 9. The composition ofclaim 8 wherein said amino compound is an alkylenepolyamine representedby the formula:

wherein U is an alkylene group of from about 2 to about 10 carbon atoms;each R is independently a hydrogen atom, a hydrocarbyl group, ahydroxy-substituted hydrocarbyl group, or an amine-substitutedhydrocarbyl group containing up to about 30 carbon atoms, with theproviso that at least one R is a hydrogen atom; and n is 1 to about 10.10. The composition of claim 8 wherein said carboxylic acylating agentis a mono- or polycarboxylic acid or anhydride containing an aliphatichydrocarbyl substituent of at least about 30 carbon atoms.
 11. Thecomposition of claim I wherein said acylated nitrogen-containingcompound is a polyisobutene substituted succinimide containing at leastabout 50 aliphatic carbon atoms in the polyisobutene group.
 12. Thecomposition of claim 1 wherein said acylated-nitrogen containingcompound has a chlorine content of no more than about 50 ppm.
 13. Thecomposition of claim 1 wherein said low-sulfur consumable lubricatingoil composition is a low-ash lubricating oil composition which furthercomprises an ash-producing detergent or dispersant.
 14. The compositionof claim 1 wherein said low-sulfur consumable lubricating oilcomposition is characterized by the absence of an ash-producingdetergent or dispersant.
 15. The composition of claim 1 wherein saidlow-sulfur consumable lubricating oil composition is comprised of atleast one ashless detergent or dispersant, corrosion-inhibiting agent,antioxidant, viscosity modifier, pour point depressant, frictionmodifier, fluidity modifier, or anti-foam agent.
 16. The composition ofclaim 1 wherein said low-sulfur consumable lubricating oil compositionhas a sulfur content of about 5 to about 50 ppm.
 17. The composition ofclaim 1 wherein said low-sulfur consumable lubricating oil compositionhas a chlorine content of no more than about 10 ppm.
 18. A method ofoperating an internal combustion engine equipped with an exhaust gasaftertreatment device, said method comprising: (A) operating said engineusing a normally liquid or gaseous fuel; (B) lubricating said engineusing a low-sulfur consumable lubricating oil composition, said oilcomposition comprising: a base oil; an acylated nitrogen-containingcompound having a substituent of at least about 10 aliphatic carbonatoms; and a sulfur content of about 5 to about 250 ppm; said oilcomposition being characterized by the absence of an extreme-pressureadditive comprised of metal and phosphorus; (C) removing part of saidlow-sulfur consumable lubricating oil composition from said engine, saidremoved part of said low-sulfur consumable lubricating oil composition(i) being combined with said fuel and consumed with said fuel as saidengine is operated or (ii) being combined with the exhaust gas from saidengine and removed from said engine with said exhaust gas; and (D)adding an additional amount of said low-sulfur consumable lubricatingoil composition to said engine to replace said removed part of saidlow-sulfur consumable lubricating oil composition.
 19. The method ofclaim 18 wherein the combination of said fuel composition and saidlow-sulfur consumable lubricating oil composition formed in step (C) iscomprised of about 0.01% to about 5% by weight of said low-sulfurconsumable lubricating oil composition.
 20. The method of claim 18wherein during step (C) said removed part of said low-sulfur consumablelubricating oil composition is introduced into said fuel composition inthe fuel tank, fuel return line, fuel injectors, intake manifold,positive crankcase ventilation system, exhaust gas recirculation system,or air intake system of the engine.
 21. The method of claim 18 whereinsaid removed part of said low-sulfur consumable lubricating oilcomposition is combined with said exhaust gas upstream of said exhaustgas aftertreatment device.
 22. The method of claim 18 wherein saidengine is a compression ignition engine.
 23. The method of claim 18wherein said fuel is a diesel fuel composition.
 24. The method of claim18 wherein said fuel composition is a low-sulfur diesel fuelcomposition.
 25. The method of claim 18 wherein said engine is a sparkignition engine.
 26. The method of claim 18 wherein said fuel is agasoline fuel composition.
 27. The method of claim 18 wherein said fuelis an unleaded gasoline fuel composition.
 28. The method of claim 18wherein said fuel is a gasoline fuel composition having a sulfur contentof up to about 300 ppm.
 29. The method of claim 18 wherein said fuel isa gasoline fuel composition having a chlorine content of no more thanabout 10 ppm.